1. Technical Field
The present invention relates to a liquid crystal device and an electronic apparatus. More particularly, the invention relates to a technique for achieving a high contrast and a wide viewing angle in a homeotropic liquid crystal device that uses liquid crystal having vertical alignment. The invention further relates to an electronic apparatus that is provided with a liquid crystal device having such enhanced features.
2. Related Art
These days, liquid crystal devices are used in a variety of electronic apparatuses such as mobile phones, hand held terminals, personal digital assistants (PDA), and the like. As one example of applications thereof, liquid crystal devices are used as display devices of electronic apparatuses that display various kinds of images. In the operation of a liquid crystal device, a voltage that is applied to a liquid crystal layer thereof is controlled on a pixel-by-pixel basis so as to control the alignment, that is, orientation, of liquid crystal molecules present in the liquid crystal layer. Light that transmits through the liquid crystal layer is modulated for each pixel by means of the alignment control of the liquid molecules. Modulated light is supplied to optical component layers such as a light polarization layer, a phase difference retardation layer, though not limited thereto, so as to display images.
Liquid crystal devices have a variety of types of operation modes. A twisted nematic (TN) mode and a vertically aligned (VA) mode are typical examples of operation modes thereof that are known in the related art. In the TN mode liquid crystal device, liquid crystal molecules are aligned in a direction that is substantially parallel to the surface(s) of a (pair of) substrate(s) when an OFF driving voltage is supplied thereto. As its name suggests, the liquid crystal molecules of the TN mode liquid crystal device have a twisted orientation toward a direction perpendicular to the substrate. On the other hand, in the VA mode liquid crystal device, liquid crystal molecules are aligned in a direction that is substantially perpendicular to the surface(s) of a (pair of) substrate(s) when an OFF driving voltage is supplied thereto. In the VA mode liquid crystal device, an orientation state where liquid crystal molecules are aligned in a direction that is substantially perpendicular to the surface of a substrate is used as black display. In other words, black display is performed when there is not any optical retardation when viewed along a normal direction with respect to the substrate. For this reason, it is possible to obtain a high contrast in the vertically aligned mode. In addition, in the vertically aligned mode, it is further possible to obtain a wide viewing angle by providing a plurality of areas that have different tilting orientations of the liquid crystal molecules that change their alignment direction at the time of the application of an ON voltage.
A related-art liquid crystal device that operates in the vertically aligned mode described above has the following electrode configuration. A set of a pixel electrode and a counter electrode, or in other words, an opposite electrode, forms each sub pixel, which constitutes a unitary display region for white display and black display. The pixel electrode is configured to have more than one dot portions (i.e., configured to have an “island-shaped” layout structure). With such a configuration, each one of the sub pixels is made up of sub dots, which constitute a plurality of dot regions. The above-described electrode configuration of the VA mode liquid crystal device of the related art is disclosed in, for example, the following publications of Japanese patent applications: JP-A-2003-43525 (specifically, refer to Page 7 and FIG. 1 thereof), JP-A-2005-345757 (specifically, refer to Page 6 and FIG. 2 thereof), and JP-A-2006-338051 (specifically, refer to Page 7 and FIG. 2 thereof).
In the VA mode liquid crystal device described above, the alignment of liquid crystal molecules is controlled by means of an oblique electric field that is generated in accordance with the planar shape of a pixel electrode as well as by the functioning of dielectric projections or slits formed on a counter electrode. When an ON voltage is applied to a liquid crystal layer, the orientation of liquid crystal molecules are changed into a direction that is specified by the alignment control. As a result thereof, a plurality of domains or multi-domains is formed. In the configuration of the VA mode liquid crystal device, each sub pixel is formed at a region where one pixel electrode and its corresponding common electrode overlap each other in a plan view. In particular, in the configuration of the VA mode liquid crystal device of the related art, a light shielding film is formed on the substrate(s) at each region that corresponds to a gap, or clearance, between two adjacent sub pixels. The light shielding film of the related art functions to prevent any light from leaking through the gap between each of adjacent sub pixels. That is, the light shutting film of the related art is provided in consideration of adverse effects that could be exerted by a voltage applied at each gap therebetween.
As described above, in the configuration of a liquid crystal device of the related art, a light shielding film is provided so as to block the leakage of light through the gap between each of sub pixels adjacent to one another in a pixel layout constituted by the plurality of sub pixels that are arrayed in a two-dimensional pattern, where each of the sub pixels is formed at a region where one pixel electrode and its corresponding common electrode overlap each other in a plan view. In the above layout configuration of the related art, the light shielding film prevents light from leaking through a peripheral region around each sub pixel, thereby further preventing the problem of contrast degradation at a level effective to some degree. The light-shutting technique described above has not been limitedly used in the VA mode liquid crystal device but also used in various types of liquid crystal devices that operate in a variety of modes other than the VA mode. Although the above-described light-shielding technique is not unique to the VA mode liquid crystal device, the intensity of an oblique electric field tends to be greater in the VA mode liquid crystal device at each peripheral region around a plurality of sub dots provided in each of the sub pixels for its functional reason. Therefore, in the configuration of the VA mode liquid crystal device of the related art, the leakage of light is likely to occur at each peripheral region around the sub dots, which causes a decrease in contrast.